Dave the flow bench uses vacuum to pull air threw the heads. the vacuum is calibrated in inches of water the flow bench used in testing uses 28 inches of water as the standard calibration the valve sizes on my big valve heads are 42 MM intakes up from 40 MM and 36 MM up from 34 MM the head work I have done to these big valve heads is not about hoging out the ports and loosing air speed. The work I have done on these heads is about increasing the air flow around the valves. the reports I have received about the high flow valve jobs to this point indicate that the low end and mid range power is improved Bob Donalds Boston engine http://www.bostonengine.com |
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